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51.
Bettina Mahler Yanina Sarquis Adamson Alejandro G. Di Giacomo Viviana A. Confalonieri Juan C. Reboreda 《Behavioral ecology and sociobiology》2009,63(11):1603-1608
The screaming cowbird Molothrus rufoaxillaris has been long known as a host specialist brood parasite. However, in the past years, the utilization of two new hosts has
been documented. We examined the variation in mitochondrial control region sequences from screaming cowbird chicks found in
the nests of two hosts, the bay-winged cowbird (Agelaioides badius), which is its regular host, and the chopi blackbird (Gnorimopsar chopi), which is a new host, in Formosa Province, Argentina. If a group of females switched to this new host, we expected to find
an association between host use and haplotype frequency distribution, indicating the presence of host-specific female lineages,
whereas we expected no such association if the cowbird population incorporated this new host and females use both hosts simultaneously.
Haplotype frequency distributions differed between cowbird chicks from the nests of both hosts. This indicates that nest choice
by females of this brood parasite is not random and that they preferentially parasitize the nests of the same host species. 相似文献
52.
Costs of brood parasitism and the lack of defenses on the yellow-winged blackbird - shiny cowbird system 总被引:2,自引:0,他引:2
The shiny cowbird (Molothrus bonariensis) is a generalist brood parasite that lays either white-immaculate or spotted egg morphs in eastern Argentina and Uruguay.
Some hosts accept both morphs, others accept spotted eggs and reject the white morph, but no host has been found to accept
white eggs and reject spotted ones. It has been suggested that the yellow-winged blackbird (Agelaius thilius) may be that type of host. The finding of a white acceptor-spotted rejector species would help to explain the occurrence
and maintenance of the parasite egg polymorphism. We studied the incidence of shiny cowbird parasitism on this host, its costs
for their reproductive success and the presence of antiparasitic defenses in the yellow-winged blackbird - shiny cowbird system.
The parasite affected the reproductive success of the host in two ways. Cowbirds punctured host eggs causing a reduction in
clutch size, and yellow-winged blackbirds deserted their nests whenever they suffered high egg loss. In addition, parasitized
nests suffered higher predation during the nestling stage, but not during egg stages, indicating that the difference found
was related to the presence of the cowbird chick, and not to higher exposure of parasitized nests to both parasites␣and predators.
Despite the costs imposed by the parasite, yellow-winged blackbirds have not evolved antiparasitic defenses. This host did
not reject any egg morph of the shiny cowbird nor desert parasitized nests unless it had suffered high egg loss. Current explanations
for the host lack of defenses, the “time lag” and the “equilibrium” hypothesis, are discussed.
Received: 29 August 1997 / Accepted after revision: 10 January 1998 相似文献
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以铜锈环棱螺(Bellamya aeruginosa)为试验对象,采用人工添加TBT的自然沉积物对铜锈环棱螺进行静态暴露实验,研究了沉积物中不同浓度TBT长期暴露(30 d)对铜锈环棱螺肝胰脏的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和谷胱甘肽(GSH)的影响,以揭示TBT对它们影响的浓度效应关系。结果表明,沉积物中低浓度(100 ng/g)TBT对SOD、CAT和GSH没有影响。当TBT浓度为500~1000 ng/g时,SOD活性呈现浓度依耐性的升高。当TBT浓度为200~1000 ng/g时,CAT活性表现为浓度依耐性的升高。高浓度(2000 ng/g)TBT则导致SOD和CAT活性急剧下降,分别比对照下降了67.33%和54.87%。当TBT浓度为200~1000 ng/g时,GSH含量呈现浓度依耐性的下降,高浓度(2000 ng/g)TBT导致GSH含量急剧下降,比对照下降了76.87%。环境水平的TBT长期暴露对铜锈环棱螺肝胰脏产生了氧化胁迫,高浓度的TBT长期胁迫使肝胰脏受到了严重的氧化损伤。CAT和GSH可以用作环境水平TBT长期暴露的有效生物标志物。 相似文献
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Nest defence behaviours, such as attacking predators and defending against predator attacks, expose birds to risk of injury
and death. However, direct costs of such behaviours are poorly documented. To evaluate potential costs of nest defence behaviours
in lesser snow geese (Chen caerulescens), we (1) estimated the proportion of interactions between arctic foxes (Alopex lagopus) and geese that resulted in physical contact and (2) examined how nest defence behaviours varied between male and female
geese. We separated interactions into attacks initiated by foxes (attacks by foxes) and attacks initiated by geese (attacks by geese). Risks associated with attacks by geese were considerably lower than the risks associated with attacks by foxes; only 1
of 1,179 attacks by geese resulted in physical contact between foxes and geese, whereas 26 of 89 attacks by foxes involved
such contact (two female geese were killed during these attacks). Attacks by geese were made almost exclusively by male geese
(>97%), whereas female geese were involved in 75% of all attacks by foxes that resulted in physical contact with geese. There
was, thus, a considerable difference in risks associated with male and female nest defence behaviours. We suggest that parental
roles during nesting (i.e., females incubate and males guard) expose female geese to greater risk of injury and death. Male
geese may, however, reduce the risk of injury or death to their mates with pre-emptive attacks on foraging foxes. 相似文献
58.
Territory and group sizes in Eurasian beavers (Castor fiber): echoes of settlement and reproduction?
Ruairidh D. Campbell Frank Rosell Bart A. Nolet Vilmar A. A. Dijkstra 《Behavioral ecology and sociobiology》2005,58(6):597-607
According to current theories of territoriality, an animal is expected to defend the smallest area that can provide resources for maximisation of reproduction, known as the economically defendable area. In group territorial species however, the strategies behind resource defence are likely to be more complex with corporate territoriality, cooperative breeding, delayed dispersal and intra-group competition all potentially playing a role. Here we examined group territoriality in a social herbivorous rodent, the Eurasian beaver Castor fiber. Beavers in our study do not inhabit economically defendable territories. Instead the sequence of arrival of pairs into unoccupied areas seems to play a more important role in determining the size of the territory, whereas group size is determined by past reproductive success. We argue that the settlement pattern and reproductive history have a lasting impact in the territorial system of beavers due to a combination of the low adult mortality, high dispersal costs, and avoidance of resource depletion.R.D. Campbell and F. Rosell contributed equally to this work 相似文献
59.
János Török Rita Hargitai Gergely Hegyi Zoltán Matus Gábor Michl Péter Péczely Balázs Rosivall Gyula Tóth 《Behavioral ecology and sociobiology》2007,61(4):541-550
Birds may influence the fitness of their offspring by transmission of different amounts of carotenoids to their eggs. Carotenoids
play crucial roles in antioxidant protection and immune defence mechanisms, but they may be available to females in limiting
amounts. Therefore, their allocation to the eggs may be influenced by the female’s condition, age and environmental circumstances.
Furthermore, the quality of the male parent, which affects the reproductive value of the offspring, may also influence this
investment. In this correlational study, we investigated proximate and ultimate factors that may lead to variation in yolk
lutein, zeaxanthin and β-carotene concentrations among and within clutches of a wild passerine, the collared flycatcher (Ficedula albicollis). We found that carotenoid concentration was positively associated with caterpillar supply at the time of egg formation,
which suggests a proximate constraint of carotenoid availability on yolk composition. Neither female condition, body size,
age, nor male plumage ornamentation, age and body size correlated with carotenoid deposition. Yolk β-carotene concentration
was found to be positively linked to yolk testosterone concentration. We suggest that females allocated more β-carotene to
their eggs to mitigate the potentially detrimental effects of elevated steroid concentration. We found that concentration
of β-carotene increased with laying order. The possible function of this pattern may be to enhance the resistance to oxidative
stress and pathogens of the disadvantaged last-hatching nestling, suggesting that collared flycatchers pursue a compensatory,
“brood survival” strategy. 相似文献
60.
Summary The production of volatile secondary plant substances during the evolution of terrestrial plants is reviewed in regard to the defensive systems of plants to microorganisms and herbivores. Plant volatiles can be produced by both anabolic and catabolic processes. Although attraction of pollinators is a well-studied phenomenon, functions of volatiles range from excretion of waste products to the production of compounds attracting natural enemies of herbivores. During the evolution of the angiosperms a diversity of volatiles were selected to defend generative parts against microorganisms. Many of these allomones were related to or even identical with sex pheromones of insects. As a result flowers of angiosperms became utilized as a mating site. Consequently insects visiting flowers became involved in pollination, facilitating the steps from anemophily to entomophily. The efficiency of entomophily was increased because of nutritional rewards.An evolutionary scenario for the impact of plant volatiles on insects is presented and the role of volatile allomones in the establishment of plant-insect relationships is emphasized by (1) their strong antimicrobial properties, (2) strategies to protect symbiotic microorganisms, (3) their function as repellents and deterrents, (4) the use of volatile allomones as kairomones. These facts speak for an adaptation of insects to plant physiology and a limited importance of phytophagous insects in selection pressure upon plants. Herbivorous insects have realized specific adaptations to be able to discriminate between complex odour blends, but the utilization of chemical groups among insect taxa is different.The main theories on plant chemical defence do not discuss the impact of volatiles on host plant selection and may be apt to revision when pheromones, allomones, kairomones and synomones are not taken into account. 相似文献